Method of processing kiln exhaust gases by chlorine bypass system and apparatus therefor

ABSTRACT

In the processing of exhaust gases by a chlorine bypass system, a portion of kiln exhaust gases G is extracted from a kiln 1, after the extracted exhaust gases G are instantly cooled to 600° C. to 700° C. or less, the dust W in the cooled exhaust gases is separated to rough powder and fine powder by a separator, the separated rough powder is returned to the kiln 1 and the separated fine powder is discharged to a cement system, wherein extracting means extracts the kiln exhaust gases at the ratio more than 0% to equal to or less than 5% and the separating point of the separator is set to 5 μm to 7 μm.

TECHNICAL FIELD

The present invention relates to a method of processing gases exhaustedfrom a kiln by a chlorine bypass system and an apparatus therefor.

BACKGROUND ART

In general, when cement clinker is calcined by a SP (suspensionpreheater) kiln or a NSP (new suspension preheater) kiln, volatilecomponents such as chlorine, alkali, sulfur etc. brought from cement rawmaterial and fuel are sequentially concentrated by circulating in thekiln preheater.

However, it is known that the circulation reaches equilibrium in a fewhours so that the amount of the volatile components brought into asystem from the cement raw material and fuel becomes equal to the amountof the volatile components taken out to the outside of the system by thecement clinker.

When a large amount of the volatile components is brought by the rawmaterial and fuel in this case, the amount of the volatile components inthe clinker is increased, by which the quality of cement is adverselyaffected.

Further, when the amount of the volatile components is increased in thesystem, since compounds of low melting point are made, the preheater isoften clogged, by which the stable operation of the kiln is obstructed.

Recently, when the effective utilization of industrial waste is promotedin particular, a raw material containing a large amount of chlorinecannot help being used, thus it is desired to effectively remove thevolatile components.

To cope with this problem, there is employed a so-called alkali bypasssystem to reduce the amount of the volatile components in the kilnpreheater system. This is a method of extracting kiln exhaust gasescontaining highly concentrated volatile components to the outside of thesystem by an alkali bypass system. Next, the alkali bypass system willbe briefly described.

Kiln exhaust gases of about 1100° C. extracted from a kiln through anextraction duct are introduced into a cooling chamber and mixed thereinwith cooling air from a fan so as to reduce the temperature of the gasesto 400 to 450° C. At the time, the compound of the volatile componentsis condensed on the surface of dust by the fall of the gas temperature.

Further, after the temperature of the gases is lowered to about 150° C.by spraying water to them in a conditioning tower, the dust in the gasesis collected by an electrostatic precipitator and remaining gases areexhausted into the atmosphere through a fan.

Although the dust is collected by the conditioning tower and theelectrostatic precipitator, since the dust contains the volatilecomponents concentrated thereto, it is disposed of as waste.

However, in the above method, since the kiln exhaust gases of about1100° C. are exhausted to the outside of the system, heat loss isgreatly increased.

Further, because a large amount of the dust is discharged to the outsideof the system and disposed of as waste, the disposal of it becomesdifficult year by year due to the shortage of places where the dust canbe disposed of and the change of the awareness of inhabitants who livein the vicinity of the places where the dust is disposed of.

In order to solve such problems, Japanese Patent No. 1835995 andJapanese Patent No. 1702995 disclose methods of reducing heat loss andthe amount of dust to be disposed of.

These patents disclose a method of setting a gas cooling temperature to600° C. to 700° C., collecting the dust in gases by a dust collector andreturning exhaust gases to a preheater exhaust gas system to therebycollect the heat thereof by as waste heat boiler so as to reduce theheat loss of the exhaust gases, and a method of cooling extracted gasesto 600° C. to 700° C., collecting the heat of the gases by a dedicatedboiler, and then collecting the dust in the gases by a dust collectorand exhausting the exhaust gases to the outside of a system. Inaddition, these patents realize reducing the absolute amount of the dustto be processed by causing the extracted gases whose temperature is madeto 600° C. to 700° C. to pass through a separator so as to return thedust having a size of 10 μm or more to a kiln as it is.

In short, a gist of the above patents is to reduce heat loss and lowerthe cost of an apparatus by finding that the temperature of extractedgases can be increased from conventional 400° C. to 450° C. to 600° C.to 700° C.

Another gist of the patents is to reduce the amount of the dust to bedisposed of by separating the dust whose size is greater than 10 μm bythe separator and returning it to the kiln by finding that alkali isomnipresent to fine particle size.

That is, this invention is embodied by correctly grasping the condensingtemperature of volatile components, discovering that a larger amount ofalkali is distributed to the fine particle size of dust, and realizingthe discovery.

The prior art intends to mainly remove alkali and a large amount of kilnexhaust gases must be extracted to achieve the object. Even if the twopatents described above are embodied, the heat loss of a kiln/preheatersystem will be about 140 to 180 J/kg-clinker in a suspension preheaterkiln and about 50 to 70 J/kg-clinker in a new suspension preheater kilnwhen 10% of kiln exhaust gases is extracted. The largest factor causingthe heat loss is that the kiln exhaust gases are extracted in a largeamount.

Further, since the amount of discharged dust is increased in proportionto the amount of the extracted gases, to employ a suitable method ofprocessing the dust is also a large problem.

Taking the above circumstances into consideration, an object of thepresent invention is to economically and stably operate a kiln with aless amount of heat loss. Another object of the present invention is tosimply dispose of fine particle dust.

DISCLOSURE OF THE INVENTION

A kiln exhaust gases processing method by a chlorine bypass systemaccording to the present invention comprises the steps of extracting aportion of kiln exhaust gases from a kiln, cooling the extracted exhaustgases to a temperature equal to or lower than the melting temperature ofa chlorine compound, separating the dust in the exhaust gases to roughpowder and fine powder by a separator, and returning the separated roughpowder to the kiln and supplying the fine powder to downstream of theseparator, wherein the ratio of the extracted amount of the kiln exhaustgases is more than 0% to equal to or less than 5%.

A kiln exhaust gases processing method by a chlorine bypass systemaccording to the present invention comprises the steps of extracting aportion of kiln exhaust gases from a kiln, cooling the extracted exhaustgases to a temperature equal to or lower than the temperature of achlorine compound, separating the dust in the exhaust gases to roughpowder and fine powder by a separator, and returning the separated roughpowder to the kiln and supplying the fine powder to downstream of theseparator, wherein the ratio of the extracted amount of the kiln exhaustgases is more than 0% to equal to or less than 5% and the particle sizeto be separated by the separator is 5 μm to 7 μm.

A kiln exhaust gases processing method by a chlorine bypass systemaccording to the present invention comprises the steps of extracting aportion of kiln exhaust gases from a kiln, cooling the extracted exhaustgases to a temperature equal to or lower than the temperature of achlorine compound, separating the dust in the exhaust gases to roughpowder and fine powder by a separator, and returning the separated roughpowder to the kiln and discharging the fine powder to the outside of thesystem, wherein the ratio of the extracted amount of the kiln exhaustgases is more than 0% to equal to or less than 5%, the particle size tobe separated by the separator is 5 μm to 7 μm and all the fine powderwhich is exhausted to the outside of the system is mixed with clinker orcement.

A kiln exhaust gases processing apparatus by a chlorine bypass systemaccording to the present invention comprises extracting means forextracting a portion of kiln exhaust gases from a kiln, cooling meansfor cooling the extracted exhaust gases to 600° C. to 700° C. or less, aseparator for separating the dust in the cooled exhaust gases to roughpowder and fine powder, and rough powder/fine powder transporting meansfor returning the separated rough powder to the kiln and supplying theseparated fine powder to downstream of the separator, wherein theextracting means extracts the kiln exhaust gases at the ratio more than0% to equal to or less than 5%, the separating point of the separator is5 μm to 7 μm, and the rough powder/fine powder transporting meanstransports all the fine powder to a clinker tank or a finishing mill.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between the bypass ratio ofkiln exhaust gases (%) and a chlorine concentration reduction ratio (%)of the present invention;

FIG. 2 is a graph showing an experimental apparatus;

FIG. 3 is a view showing the result of an experiment;

FIG. 4 is a graph showing the relationship between the particle size(μm) of dust and a cumulative size distribution (%);

FIG. 5 is a graph showing the relationship between the dust additiveratio (5) in a chlorine bypass system and the 28 days compressivestrength of cement mortar (-);

FIG. 6 is a view showing a first embodiment of the present invention;

FIG. 7 is a view showing a second embodiment of the present invention;

FIG. 8 is a view showing a third embodiment of the present invention;

FIG. 9 is a view showing a fourth embodiment of the present invention;

FIG. 10 is an enlarged perspective view of the indirect type air coolerof FIG. 9; and

FIG. 11 is a view showing a fifth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The inventors eagerly studied the above problems of the prior art andexamined first which of volatile components, which obstacle the stableoperation of a kiln most obstacles it. As a result, the inventors foundthat chlorine most keenly affected the stable operation of the kiln.That is, the inventors found that although the content of chlorine wasonly about one tenth of alkali and sulfur in the components contained inclinker, the delicate change of concentration of the chlorine keenlyaffected the creation of a coating on a preheater and consequently thestable operation of the kiln.

The inventors examined a method of effectively removing chlorine basedon the knowledge. As a result, it was found that a large reduction ratioof chlorine (curve A) could be obtained in a small amount of extractionas compared with alkali (curves B, C) as shown in FIG. 1. In FIG. 1, theaxis of ordinates represents a concentration reduction ratio (%) and theaxis of abscissas represents a bypass ratio (%), in which the valuesshown by them are represented by logarithm.

That is, it was found that 98% or more of chlorine could be removed byextracting 10% of kiln exhaust gases. In addition, it was found thatsince an alkali removing ratio was about 10% at the time, the extractionamount of the exhaust gases could be greatly reduced by making good useof the above-mentioned. In the experiment, the relationship between theextraction amount of kiln exhaust gases α% and the reduction ratio ofchlorine β% (the reduction ratio of chlorine per 1% of a kiln extractionamount) was β=50% when 0%<α<1%, β=8.5% when 1%<α<5% and β=1.4% when5%<α<14%. Therefore, the reduction ratio of chlorine reached 90% whenthe extraction amount of the kiln exhaust gases was about 5%, thus itwas found that a sufficient effect could be achieved by the extractionamount of 5% as a result of the consideration of economical efficiencyand practicality.

Further, the inventors examined the bypass ratio (%) and the removalratio (%) of chlorine and alkali by making a simple chlorine/alkalicirculation model shown in FIG. 2.

In the model, a cement raw material M was charged into a kiln RK througha preheater PH and a portion of the chlorine and alkali (sodium andpotassium) in the raw material M was volatilized and circulated in thekiln together with exhaust gases KG and the other of them was dischargedto the outside of the kiln together with clinker CK.

When the volatility of chlorine and alkalies in the raw material M ε₁and the volatility of circulating chlorine and alkalies ε₂ of thechlorine and alkali in the raw material M was examined by theexperimental apparatus, that is, when the case that the chlorine andalkali were volatilized while circulated in a kiln and condensed andthen volatilized again was examined, the result of the examination waschlorine ε₁ =ε₂ =0.995, sodium ε₁ =0.2, ε₂ =0.8, potassium ε₁ =0.4, ε₂=0.9.

That is, the volatility factor ε₁ of chlorine=99.5% was much larger thanthe volatiity factor ε₂ of alkali (sodium 20%, potassium 40%).Therefore, the ratio of chlorine discharged to the outside of the kilnwas 0.5% which was much smaller than that of alkali.

Since almost no chlorine was discharged to the outside of the kiln asdescribed above, the concentration of the chlorine in the kiln wasgreatly thickened as compared with that of alkali, by which a coatingwas formed.

Next, when kiln exhaust gases were extracted through a bypass BP formedto the vicinity of the inlet IN of the kiln and the extraction ratio(bypass ratio) (%) thereof and the removal ratio (%) thereof, which hadthe same meaning as the above concentration reduction ratio, weremeasured, the result shown in FIG. 3 was obtained.

In FIG. 3, a curve A1 represents chlorine, a curve B1 representspotassium and a curve C1 represents sodium, respectively. As apparentfrom FIG. 3, as to alkali (sodium C1, potassium B1), the bypass ratiowas approximately in direct proportion to the removal ratio in the rangeof 0 to 10% of the bypass ratio. However, the removal ratio was as lowas about 10% to 20% even if the bypass ratio was 10%. On the other hand,the high removal ratio of 60% or more could be obtained as to chlorineA1 even if the bypass ratio was as low as 2% or less, and the removalratio of 90% could be obtained when the bypass ratio was 5%.

Note, there are known the following relations which represent therelationship between the removal ratio X of chlorine/alkali and thebypass ratio v thereof. (ε₁ +Xε₂) (1-v)=removal ratio X removal ratioX=ε₁ (1-v)/ {1-ε₂ (1-v)} removal ratio X=100(ε₁ +Xε₂)v

From the relations, it can be found that when the volatility factors ε₁,ε₂ are higher, the bypass ratio v may be smaller to obtain a certainamount of the removal ratio X.

It is found from the above relations that it is preferable that thevolatility factors ε₁, ε₂ are as high as possible to obtain the removalratio x of constant.

Further, it was found in the above process that chlorine (curve D) wasmore omnipresent to fine powder than alkali (curve E) as shown in FIG.4. Note, a curve F represents the cumulative size distribution of aparticle size of dust, the axis abscissas represents a particle size(μm) and the axis of ordinates represents a cumulative size distributionof a particle size (%), respectively.

As a result, when attention was paid only to the removal of chlorine, itwas found that when extracted gases after cooling were caused to passthrough a separator, a sufficient reduction ratio of chlorine could beobtained by a particle size of about 5 to 7 μm different from theparticle size 10 μm which was used in the alkali bypass system. Anamount of waste dust could be reduced in a chlorine bypass system ascompared with the alkali bypass system due to this knowledge. The amountof waste dust was made to 0.1% or less of the quantity of production bythe kiln from the above-mentioned.

The waste dust is conventionally taken out to the outside of the systemand reclaimed or washed with water to remove alkali therefrom and thenused as a part of a cement raw material. This is because of the reasonthat since a lot of dust is discharged in the case of the alkali bypasssystem, when the dust is returned to the system as it is, it adverselyaffects the quality of cement.

The inventors of the present invention studied what degree of chlorinebypass dust added to cement adversely affected the quality thereof bytaking the above point into consideration and FIG. 5 shows the result ofthe study.

According to FIG. 5, it could be found that the addition of the chlorinebypass dust using the present invention to cement in an amount exceeding0.1% greatly lowered the 28 days compressive strength of cement mortarwhich was an important index indicating the quality of cement. Fromthis, it could be found that no problem was caused in quality by theaddition of 0.1% or less of the chlorine bypass dust to cement. In FIG.5, the axis of ordinates represents the 28 days compressive strength (-)of cement mortar and the axis of abscissas represents the additive ratio(%) of the chlorine bypass dust.

Since the quantity of production of clinker made by a cement kiln isusually in direct proportion to the quantity of production of cement andthe quantity of the dust discharged by the chlorine bypass systemaccording to the present invention is less than 0.1% of the quantity ofproduction of the clinker, even if the entire amount of the dust ismixed with the cement, the quality of the cement is not degraded.

Since all the amount of dust cannot be added to cement in theconventional alkali bypass system because the system discharges a lot ofdust, the method of adding all the amount of dust can be realized forthe first time by the employment of the present invention.

EMBODIMENT 1

A kiln exhaust gases processing apparatus by a chlorine bypass system ofa first embodiment of the present invention will be described withreference to FIG. 6. When chlorine is bypassed, kiln exhaust gases G areextracted from the inlet of a rotary kiln (or also called kiln) 1 to anot shown preheater by an extraction duct 2. The position where theexhaust gases are extracted is preferably as far as possible from theposition to which a raw material flows and, for example, a kiln risingduct 1a is selected as the position. This is because the extraction duct2 is difficult to be damaged when the position of extraction duct is asfar as possible from the raw material flowing position and becausechlorine has a high concentration. The kiln exhaust gases are extractedat the ratio greater than 0% to equal to or less than 5%.

After the kiln exhaust gases G extracted from the extraction duct 2 arequickly cooled instantly to the melting point of a chlorine compound,that is, to 600 to 700° C., they are separated by a separator 8, forexample, a cyclone type separator. When it is supposed that the quantityof production of clinker in a suspension preheater kiln or a newsuspension heater kiln is represented by a kg, an apparatus excellent ineconomical efficiency and effectiveness can be obtained when the crosssectional area of the cyclone main body of the cyclone type separator isset to a×7.55×10⁻³ m² or less and preferably to the range of a×5×10⁻⁴ m²to a×5×10⁻³ m².

The separating point of the separator 8 is set to 5 to 7 μm and powderexceeding the separating point is returned to a kiln 1 as it is. Afterthe gases G containing fine powder of 5 to 7 μm or less are subjected toheat exchange through a boiler 9, the dust contained therein iscollected by a dust collector 6 and then the gases G are exhausted tothe atmosphere. Dust W having a large content of chlorine which iscollected by the boiler 9 and the dust collector 6 are discharged to theoutside of a cement kiln system. The dust W containing chlorine in thehigh concentration is transported to a cement finishing mill system bysuitable transportation means 10, for example, a truck, an air conveyingvehicle, air transportation means, a belt conveyer, a chain conveyer orthe like.

The above transported dust W is mixed with the clinker 14 in a clinkertank 18 which is calcined out from the kiln 1 through a primary storagebin 11a, feed equipment 12b and transportation means 13. Note, the dustW may be supplied to a storage bin lib in which the clinker is stored,supplied to a finishing mill 20 or supplied to and mixed with cement 17discharged from the finishing mill 20.

EMBODIMENT 2

An embodiment 2 of the present invention will be described withreference to FIG. 7. In the embodiment 2, kiln exhaust gases G of hightemperature extracted from a kiln exhaust gases extraction duct 2 aredirectly introduced to a separator 8, for example, a cyclone, andseparated while cooled to 600° C. to 700° C. which is the melting pointof a chlorine compound.

A cooling method is such that cooling air CL is introduced from theinlet or the body 8a of the cyclone 8 to instantly cool the gases. Aprocess to be executed thereafter is the same as that of the embodiment1.

EMBODIMENT 3

An embodiment 3 of the present invention will be described withreference to FIG. 8. The embodiment 3 shows another method of theexhaust gases processing method in the embodiment 2. After fine powderdust containing chlorine of high concentration is collected from kilnexhaust gases G, which have passed through a separator 8, by a dustcollector capable of processing the exhaust gases G even at hightemperature, for example, a moving bed dust collector 22, the exhaustgases G are returned to the exhaust gases of a kiln preheater pipe 23and the heat thereof is collected by a waste heat boiler 24 providedwith the apparatus. Note, numeral 25 denotes a calciner, numeral 26denotes a preheater, numeral 27 denotes an induced draft fan, and asymbol S denotes the cyclone of the preheater 26, respectively.

EMBODIMENT 4

A fourth embodiment of the present invention will be described withreference to FIG. 9 and FIG. 10. The embodiment 4 shows still anotherexhaust gases processing method in the embodiment 2.

Although the fine powder in exhaust gases G must be separated after therough particles therein are separated by a separator 8, since the gaseshave a high temperature of 400° C. to 500° C. at this stage, the dustcontained in the gases cannot be separated by an ordinary dust collectorwithout the use of, for example, a moving bed dust collector whichpermits the dust in the exhaust gases to be collected as it is and theexhaust gases to be returned to a kiln system so that the waste heatthereof can be collected by a waste heat boiler.

To cope with this problem, conventionally, the temperature of the gasesis lowered and the heat thereof is collected by spraying water orinstalling a small boiler.

However, the method of lowering the temperature by spraying water cannotbe used because it makes the use of dust to cement difficult. Thus,there is used a device using cool air, for example, an indirect type aircooler, a cooling air mixing type cooler or the like which indirectlyexecutes cooling.

The indirect type air cooler will be described. As shown in FIG. 10, theair cooler 28 is made combining the passage 81 for dust containing gasesG and the passage 82 for cooling air so as to lower the temperature ofthe dust containing gases G to 200° C. or less by the cooling air CL.

Although this type of indirect cooling is ordinarily executed by usingwater as a cooling medium, the use of water in the present inventioncauses condensation on a boundary surface or increases humidity, thusthere arises a trouble of clogging a cooling machine by the adhesion ofa chlorine compound which is deliquescent.

However, the use of cooling air as the cooling medium can lower thetemperature of the dust containing gases without the occurrence of theabove trouble.

EMBODIMENT 5

An embodiment 5 of the present invention will be described withreference to FIG. 11. The embodiment 5 is different from the embodiment1 in that an air mixing type cooler 93 similar to the above cooler 3 isinterposed between a separator 8 and a dust collector 6.

The embodiments of the present invention are not limited to the abovearrangements but, for example, the cooling air CL may be supplied to thecooler 3 in an amount larger than that in the other embodiments and thekiln exhaust gases G may be introduced to the separator 8 after thetemperature thereof is lowered to 200° C. or less.

As apparent from the above description, the present invention achievesthe following remarkable advantages:

(1) since the extraction ratio of the kiln exhaust gases is set to morethan 0% to equal to or less than 5%, almost all the chlorine can beremoved and as a result, a rotary kiln can be stably operated andchlorine can be effectively removed with a minimum amount of heat loss;

(2) since an amount of gases to be extracted in the chlorine bypasssystem is smaller than that extracted in the alkali bypass system, thesize of the processing apparatus can be reduced, thus both the space andthe cost of the apparatus can be reduced, whereby the kiln can be stablyand economically operated; and

(3) since the amount of the gases extracted by the kiln is smaller thanthat extracted by prior art and since the separating point of theseparator is small, the amount of the exhaust dust can be greatlyreduced.

As a result, since the amount of dust can be reduced to such a degree ascauses practically no problem in the quality of cement even if the dustis mixed with cement by being caused to bypass the kiln in place ofbeing exhausted to the outside of the cement system, a process forreclaiming the dust can be omitted.

Further, since the amount of the dust is very small as compared withthat in the prior art, even if the dust is reclaimed or washed withwater, a cost for processing it is very low, thus the present inventionis advantageous from a view point of economic efficiency.

We claim:
 1. A kiln exhaust gases processing method by a chlorine bypasssystem, comprising the steps of:extracting a portion of kiln exhaustgases from a kiln between a kiln inlet and preheater, where volatilecomponents are concentrated; cooling the extracted exhaust gases to atemperature equal to or lower than the melting temperature of a chlorinecompound; separating the dust in the exhaust gases to rough powder andfine powder by a separator; and returning the separated rough powder tothe kiln and supplying the fine powder to downstream of the separator,wherein the ratio of the extracted amount of the kiln exhaust gases ismore than 0% to equal to or less than 5%.
 2. A kiln exhaust gasesprocessing method by a chlorine bypass system, comprising the stepsof:extracting a portion of kiln exhaust gases from a kiln between a kilninlet and preheater, where volatile components are concentrated; coolingthe extracted exhaust gases to a temperature equal to or lower than themelting temperature of a chlorine compound; separating the dust in theexhaust gases to rough powder and fine powder by a separator; andreturning the separated rough powder to the kiln and supplying the finepowder to downstream of the separator, wherein the ratio of theextracted amount of the kiln exhaust gases is more than 0% to equal toor less than 5% and the particle size to be separated by the separatoris 5 μm to 7 μm.
 3. A kiln exhaust gases processing method by a chlorinebypass system, comprising the steps of:extracting a portion of kilnexhaust gases from a kiln between a kiln inlet and preheater, wherevolatile components are concentrated; cooling the extracted exhaustgases to a temperature equal to or lower than the melting temperature ofa chlorine compound; separating the dust in the exhaust gases to roughpowder and fine powder by a separator; and returning the separated roughpowder to the kiln and supplying the fine powder to downstream of theseparator, wherein the ratio of the extracted amount of the kiln exhaustgases is more than 0% to equal to or less than 5%, the particle size tobe separated by the separator is 5 μm to 7 μm and all the fine powder ismixed with clinker or cement.
 4. A kiln exhaust gases processingapparatus by a chlorine bypass system, comprising:extracting means,positioned between a kiln inlet and preheater, where volatile componentsare concentrated, for extracting a portion of exhaust gases from a kiln;cooling means far cooling the extracted exhaust gases to 700° C. orless; a separator for separating the dust in the cooled exhaust gases torough powder and fine powder; and rough powder/fine powder transportingmeans for returning the separated rough powder to the kiln and supplyingthe separated fine powder to downstream of said separator, wherein saidextracting means extracts the kiln exhaust gases at the ratio more than0% to equal to or less than 5%, the separating point of said separatoris 5 μm to 7 μm, and said rough powder/fine powder transporting meanstransports all the fine powder to a clinker tank or a finishing mill. 5.A kiln exhaust gases processing apparatus by a chlorine bypass systemaccording to claim 4, wherein said separator is a cyclone separator. 6.A kiln exhaust gases processing apparatus by a chlorine bypass systemaccording to claim 5, wherein said cyclone separator has cylindricalparts of cyclone whose cross sectional area is set to a×7.55×10⁻³ m² orless supposing that the kiln has a clinker calcining capacity of akg/minute.
 7. A kiln exhaust gases processing apparatus by a chlorinebypass system according to claim 4, wherein said separator communicateswith a dust collector through an indirect type air cooler.
 8. A kilnexhaust gases processing apparatus according to claim 4, wherein saidseparator communicates with a dust collector through a cooling airmixing type air cooler.
 9. A kiln exhaust gases processing apparatus bya chlorine bypass system according to claim 4, wherein said separator isa moving bed dust collector.